Emergy Evaluation of Water Management in the Florence Area

EMERGY SYNTHESIS 5: Theory and Applications of the Emergy Methodology Proceedings from the Fifth Biennial Emergy Conference, Gainesville, Florida Edited by Mark T. Brown University of Florida Gainesville, Florida Managing Editor Sharlynn Sweeney University of Florida Gainesville, Florida Associate Editors Daniel E. Campbell US EPA Narragansett, Rhode Island Shu-Li Huang National Taipei University Taipei, Taiwan Enrique Ortega State University of Campinas Campinas, Brazil Torbjorn Rydberg Centre for Sustainable Agriculture Uppsala, Sweden David Tilley University of Maryland College Park, Maryland Sergio Ulgiati Parthenope University of Napoli Napoli, Italy December 2009 The Center for Environmental Policy Department of Environmental Engineering Sciences University of Florida Gainesville, FL ii 32 Emergy Evaluation of Water Management in the Florence Area Federico M. Pulselli, Riccardo M. Pulselli, Nicoletta Patrizi and Nadia Marchettini ABSTRACT The paper presents the results of a project on the Province of Florence (Italy), investigating the availability and use of water resources by emergy evaluation. The study is devoted to the analysis of the watershed of the Sieve River, tributary of River Arno that feeds Florence and its surroundings. Along the river an artificial basin has been created by means of the Bilancino dam to preserve water quantity and quality, and to protect the Florentine area from dangerous periodical inundations. Different specific emergies of water can be identified along the course of the river, especially before and after the Bilancino dam. The aqueduct system of the province of Florence is fed by several rivers and torrents. Here we consider Stura, Sieve and Arno rivers. It is fragmented and divided into many subsystems, slightly interacting with each other. Hence, different systems of extraction and distribution of water are chosen on the basis of their dimension, type and location, and evaluated in order to calculate the specific emergy of water in different infrastructural contexts. The emergy investment necessary to implement different water management strategies is evaluated, focusing on the role and use of resources under a sustainability viewpoint. INTRODUCTION Water resources have been the core of the development of every process of civilization. Mankind has long tried manners to capture, store, clean and distribute fresh water resources as well as to reduce its vulnerability. Agriculture and industrial activities as well as urban development are made possible by the presence of water and require the implementation of water management systems (Gleick, 2000). From the environmental viewpoint, water management means to reduce pumping from natural storage, reintroduce water as near as possible to its extracting zones and with characteristics as similar as possible to natural ones (Fugaro et al., 2002). Furthermore, according to sustainability criteria, also environmental values and social and cultural implications of human activity have to be involved into the decision-making process, particularly in regard to long-term effect (Helström et al., 2000). This paper presents the results of an environmental assessment of water in the Sieve watershed in the Province of Florence (Italy). An emergy based environmental accounting system (Odum, 1988, 1996) has been implemented. Emergy evaluation takes into account all material and energy flows necessary to obtain a certain product (in this case, water). Emergy can be used to evaluate different aspects of the study of water systems: properties and peculiarities, availability, conservation and sustainable use. See, for example, Odum, 1996 and Odum and Arding, 1991 for the evaluation of chemical potential energy and geopotential energy of water. Fugaro et al., (2002) and Vassallo et al. (2006) presented the results of emergy evaluation of two watershed systems in Italy. Other assessments of water systems and watershed management were also performed through emergy analysis by Odum et al. (1997), Romitelli (2005), Tilley and Brown (2006), Blancher et al. (2007), Agostinho et al. (2008), and Chen et al. (2009). Emergy has been also used to account for the impact of infrastructures 355 necessary to manage water (like dams or rivers diversions) (Brown and McClanahan, 1996, Martin, 2002; Kang & Park, 2002), and the metabolism of rivers (Chen et al., 2009). A dissertation on the value of water and the allocation of water resource at different geographical scales is reported in Buenfill (2001). The analysis presented here has been divided into two parts: the first one takes into account the inputs that feed the flow of water at a given point of the river; the second one takes into account the inputs that support drinkable water production and distribution. The emergy evaluation of water in the river gives an estimation of the work of the ecosystem in making water “naturally” available in different points of the river. This value, expressed in terms of specific emergy of water, is then used, together with the value of all other inputs (e.g. the aqueduct system), to calculate the environmental cost of providing water to the finals consumers. Different site-specific values of emergy per unit mass are calculated and discussed. MATERIALS AND METHODS Sieve River is the main right tributary of the Arno River, that feeds the city of Florence and its surroundings. It can be considered as a torrent since it alternates low and high flows of water. Along the river, an artificial basin was created by means of a dam in order to preserve water quantity and quality and protect the Florentine area from possible dangerous floods. In fact, in 1966 a dramatic flood hit the city causing victims and enormous damages. This artificial basin, called Bilancino lake and located in the area of an ancient Pleistocene lake, has an area of 5 km2 and stores 84x106 m3 of water (ARPAT, 2005). River Stura Stura plant River Sieve (Sieve Alta) Bilancino Bilancino DAM lake River Sieve Anconella plant Pontassieve plant River ARNO Figure 1. The area of analysis: River Sieve watershed (as a portion of the larger Arno watershed) in Tuscany, Italy. Specific emergies of water along the rivers of the area – Stura, Sieve and Arno – were calculated (white circles). Specific emergies of water distributed were calculated for three different plants (Stura, Pontassieve and Anconella plants). 356 The dam was built after some decades of political struggles. It is mainly made by 2,000,000 m3 of natural materials locally available, such as diabasic rockfill, limestone rockfill, gravel, sandstone and clay, with an expected life of 200 years. The contribution of reinforcing concrete was considered as negligible in the emergy analysis. Figure 1 shows the area under study, namely river Sieve watershed and a portion of the course of river Arno. Investigation was conducted in order to assess the value of water along the course of the rivers of the area. Four white circles represent the points where the specific emergy of water was calculated: Two points are along the river Sieve (upstream and downstream of Bilancino lake, respectively); two more points are along the river Stura (upstream of the lake) and along the river Arno (in the city of Florence). The choice of the points was due to two reasons: (a) the presence of the Bilancino lake and the dam, that contribute to manage the flow of water and affect its emergy value; (b) the structure of local water distribution network which is composed by several aqueducts of different size (in terms of infrastructure and water collected and distributed), slightly interacting with each other and fed by different points of water extraction. For these reasons, since water has not the same environmental value along the course of a river, the analysis of aqueduct systems was performed in the proximity of points of the rivers previously analyzed (water collection points). In fact, three of the four white circles in Figure 1 coincide with plants/aqueduct systems, namely Stura, Pontassieve and Anconella plants (represented by white boxes placed upon circles). The energy diagram is shown in Figure 2. It provides a general overview of the system and its main components. The boundaries of the system are represented by the larger rectangle. The grey box represents Sieve watershed, including the tributaries of river Sieve, the dam and Bilancino lake located along the course of the river. These components, together with natural environmental inputs (sun, rain, wind, geothermal heat and basic flow/spring water), affect the value of water. Downstream of Bilancino Lake, river Sieve drains into Arno. Water in the rivers is represented by storages since it has to be maintained. Along the course of water, from Sieve river to Bilancino lake and Arno river, three points of water withdrawing are represented as splits. Arrows going to the aqueduct system represent all the inputs (including water collected) necessary to purify and distribute water. The diagram, from left to right, describes the course of water in all its phases, represented in series: water flows from a reservoir to another and is withdrawn at different points. In each point of the watershed, water assumes different environmental values. In calculating the emergy value of water in different points, natural components as well as anthropic infrastructures and energy (goods and services) necessary to make water available were taken into account. In particular: the dam contributes to maintain the flow of water and it was included in the analysis in terms of materials and costs; the aqueduct system produces and distributes drinkable water to people and was considered in terms of the mass and energy involved in all the processes (electricity, human work, machineries, pipes, concrete, sand and money). Water is distributed to people, who pay money for this service. RESULTS AND DISCUSSION Emergy evaluation of water in the rivers The presence and availability of water along the course of the rivers depend on natural components and, downstream of Bilancino lake, on the presence of the dam, as a structural component of the system.

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